pay off his balance in $4$ years using automatic payments sent at the end of each month.

a$.$ What monthly payment must he make to pay off the account at the end of $4$ years?

b$.$ How much total interest will he have paid?

a$.$ What monthly payment must he make to pay off the account at the end of $4$ years?

$($Round to the nearest cent as needed$)$

b$.$ How much total interest will he have paid?

$($Round to the nearest cent as needed$)$